Use scientific notation for big values in labeled slider

[Czaki]

Closes #224

Use QLabel instead of QDoubleSpinBox for custom representation of big/small values.

[codecov]

Codecov Report

Attention: Patch coverage is 81.31868% with 17 lines in your changes missing coverage. Please review.

Project coverage is 86.80%. Comparing base (358d041) to head (83319e7).

Files with missing lines	Patch %	Lines
src/superqt/sliders/_labeled.py	81.31%	17 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #226      +/-   ##
==========================================
- Coverage   87.14%   86.80%   -0.35%     
==========================================
  Files          49       49              
  Lines        3774     3835      +61     
==========================================
+ Hits         3289     3329      +40     
- Misses        485      506      +21     

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[tlambert03]

basic idea looks good. lemme know when ready for a full review. How do you plan to manage when it switches into scientific notation?

[Czaki]

Currently, it depends on str(float), as for big values, on my machine it uses scientific notation. I need to check how universal it is.

[tlambert03]

hey @Czaki, gentle ping on this PR. still interested in adding this?

[Czaki]

Yes. But I'm not sure if I will find time before January (Christmas etc).

[tlambert03]

K, no hurry. Enjoy

[jiban]

Hi @Czaki,
Thank you for the implementation.
By the way, I've looked for an explicit specification that stated str(float) used scientific notation when necessary (i.e General Format, 'g')
I could not find that statement but at least I found that cpython implementation was working like that.
str(float) uses General Format by default.

Here are what I found.
I hope it helps you save time.

1. From Python Doc. for str()

   str(object) returns type(object).__str__(object), which is the “informal” or nicely printable string representation of object. For string objects, this is the string itself. If object does not have a __str__() method, then str() falls back to returning repr(object).

   so str(float) will call float.__str__() or float.__repr__()

2. Python float does not have __str__() but have __repr()__. See PyTypeObject PyFloat_Type.

3. float_repr() which float.__repr__ is mapped to calls PyOS_double_to_string() with format_code of 'r'.

   static PyObject *
   float_repr(PyFloatObject *v)
   {
       PyObject *result;
       char *buf;
   
       buf = PyOS_double_to_string(PyFloat_AS_DOUBLE(v),
                                   'r', 0,
                                   Py_DTSF_ADD_DOT_0,
                                   NULL);
       if (!buf)
           return PyErr_NoMemory();
       result = _PyUnicode_FromASCII(buf, strlen(buf));
       PyMem_Free(buf);
       return result;
   }

4. Finally, PyOS_double_to_string() uses 'g'(General Format) option for 'r' format code.

   case 'r':          /* repr format */
   /* Supplied precision is unused, must be 0. */
   if (precision != 0) {
       PyErr_BadInternalCall();
       return NULL;
   }
   /* The repr() precision (17 significant decimal digits) is the
      minimal number that is guaranteed to have enough precision
      so that if the number is read back in the exact same binary
      value is recreated.  This is true for IEEE floating point
      by design, and also happens to work for all other modern
      hardware. */
   precision = 17;
   format_code = 'g';
   break;

so, I think your choice of using str(float) is good.

Thank you.

-- Jake

[Czaki]

@tlambert03 may you take a look on the implementation of setValue to tell what did you think about the logic to converting to string?

Maybe the minimum and maximum limits should be more flexible:

superqt/src/superqt/sliders/_labeled.py

Lines 679 to 683 in 358d041

	if opt == EdgeLabelMode.LabelIsRange:
	self.setMinimum(-9999999)
	self.setMaximum(9999999)
	with contextlib.suppress(Exception):
	self._slider.rangeChanged.disconnect(self.setRange)

[tlambert03]

may you take a look on the implementation of setValue to tell what did you think about the logic to converting to string?

seems reasonable to me i think? Maybe a few more tests would help clarify whether it's doing what you want?

Maybe the minimum and maximum limits should be more flexible:

sure, seems reasonable

[tlambert03]

typo _editig_finished -> _editing_finished